Erratic results from metrics
----------------------------
Key: HTTPCORE-254
URL: https://issues.apache.org/jira/browse/HTTPCORE-254
Project: HttpComponents HttpCore
Issue Type: Bug
Affects Versions: 4.1
Reporter: Sebb
The values obtained from getMetrics are erratic. For example, the following
code:
DefaultHttpClient httpclient = new DefaultHttpClient();
try {
HttpRequestBase req = new
HttpGet("http://wiki.apache.org/jakarta-jmeter/JMeterCommitters";);
for(int i = 0; i<3;i++) {
HttpContext localContext = new BasicHttpContext();
HttpResponse rsp = httpclient.execute(req, localContext);
System.out.println(rsp.getStatusLine());
HttpConnection conn = (HttpConnection)
localContext.getAttribute(ExecutionContext.HTTP_CONNECTION);
HttpConnectionMetrics metrics = conn.getMetrics();
long hdr = metrics.getReceivedBytesCount();
System.out.println("hdr "+hdr);
HttpEntity entity = rsp.getEntity();
// Thread.sleep(1500);
if (entity != null) {
EntityUtils.consume(entity);
}
long total = metrics.getReceivedBytesCount();
System.out.println("tot "+total);
metrics.reset();
}
} finally {
// When HttpClient instance is no longer needed,
// shut down the connection manager to ensure
// immediate deallocation of all system resources
httpclient.getConnectionManager().shutdown();
}
}
May produce:
HTTP/1.1 200 OK
hdr 284
tot 566
HTTP/1.1 200 OK
hdr 283
tot 313
HTTP/1.1 200 OK
hdr 283
tot 313
Enabling the sleep produces more consistent (but still inaccurate) results:
HTTP/1.1 200 OK
hdr 284
tot 10946
HTTP/1.1 200 OK
hdr 283
tot 10945
HTTP/1.1 200 OK
hdr 283
tot 10945
Rather unexpected behaviour, but as it happens, a very simple cause:
// AbstractSessionInputBuffer lines 184-189
// If the remaining capacity is big enough, read directly from the
// underlying input stream bypassing the buffer.
if (len > this.minChunkLimit) {
return this.instream.read(b, off, len);
} else {
// otherwise read to the buffer first
The code also bypasses the metrics collection...
Fixing this results in the following (with or without the sleep):
{noformat}
HTTP/1.1 200 OK
hdr 284
tot 16643
HTTP/1.1 200 OK
hdr 283
tot 16642
HTTP/1.1 200 OK
hdr 283
tot 16642
{noformat}
[Note that the slight variation in size is due to a minor change in the
headers.]
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